HYBRID ELECTRIC TURBOCHARGER FOR EXHAUST ENERGY RECOVERY AND TRANSIENT LAG REDUCTION

The United States economy and the American way of life rely heavily on transportation by cars and trucks. This transportation is dependent almost entirely on oil, which creates vulnerability to supply chain disruptions, potential for fuel price shocks, and exposure to emission of air pollutants. Reducing vehicular fuel consumption is critical for sustaining United States economic and environmental well-being. Under this program, the Department of Energy is supporting the development of innovative engine-boosting technologies that will provide these fuel- saving benefits for both passenger cars and commercial trucks. A hybrid-electric turbocharger that incorporates an integrated motor/alternator onto the turbocharger shaft is being developed that is capable of generating electrical power at high speed/load conditions or during deceleration, improving transient response (turbo lag), and broadening the effective range of the turbocharged engine. The overall objective is to demonstrate a functional prototype and production-level design at the conclusion of Phase II that exceeds Department of Energy targets for fuel economy, operating range, and cost. A hybrid-electric turbocharger design was completed during the Phase I effort. This effort included design and analysis of an 11 kW integrated motor/alternator capable of the required torque assistance to the turbocharger for transient lag reduction. A complete housing for the motor/alternator was designed, computationally optimized, fabricated, and experimentally tested during the Phase I effort as well. Detailed engine/vehicle simulations showed that a commercial truck equipped with the hybrid-electric turbocharger met the Department of Energy goals for fuel economy improvement and operating range expansion. During the Phase II effort, the Phase I design effort will be built upon by fabricating the motor/alternator and assembling the hybrid-electric turbocharger. A power electronics system for controlling the turbocharger will be developed, and the completed prototype will be tested on an engine. A control strategy to optimize fuel consumption, control emissions, and improve drivability will be investigated. The design will also be optimized for production-level manufacturing methods. Commercial Applications and Other Benefits The market for automotive turbochargers is large and growing; the global market size was approximately $1.9B in 2010 and is expected to grow to $2.9B by 2015. Taking advantage of the trend toward downsized turbocharged engines, a next-generation turbocharger with unparalleled benefits to the consumer in terms of both fuel economy and driving experience will be provided.